include ../../../../_includes/_util-fns

:marked
  Everything that we can do in Angular 2 in TypeScript, we can also do
  in JavaScript. Translating from one language to the other is mostly a
  matter of changing the way we organize our code and the way we access
  Angular 2 APIs.
  
  在Angular 2中，所有能用TypeScript完成的事，也都能用JavaScript完成。
  从一个语言换成另一个语言，最多只会影响源代码的组织方式和访问Angular 2 API的方法。

  Since TypeScript is a popular language option in Angular 2, many of the
  code examples you see on the Internet as well as on this site are written
  in TypeScript. This cookbook contains recipes for translating these kinds of
  code examples to ES5, so that they can be applied to Angular 2 JavaScript
  applications.
  
  TypeScript是个广受欢迎的Angular 2语言选项，你在网络上和本站上看到的很多范例代码都是用TypeScript写的。
  本烹饪宝典包含如何把这些代码编译到ES5的菜谱，这样它们就可以被用到JavaScript版的Angular 2程序里了。
  

<a id="toc"></a>
:marked
  ## Table of contents
  
  ## 目录

  [Modularity: imports and exports](#modularity)
  
  [模块化：导入与导出](#modularity)

  [Classes and Class Metadata](#class-metadata)
  
  [类和“类的元数据”](#class-metadata)
  
  [Input and Output Metadata](#property-metadata)
  
  [`Input`(输入)与`Output`(输出)元数据](#property-metadata)
  
  [Dependency Injection](#dependency-injection)
  
  [依赖注入](#dependency-injection)
  
  [Host and Query Metadata](#other-property-metadata)
  
  [`Host`(宿主)与`Query`(查询)元数据](#other-property-metadata)

  **Run and compare the live <live-example name="cb-ts-to-js">TypeScript</live-example> and <live-example name="cb-ts-to-js" lang="js">JavaScript</live-example>
  code shown in this cookbook.**
  
  **运行并比较本烹饪宝典里的在线<live-example name="cb-ts-to-js">TypeScript</live-example>和<live-example name="cb-ts-to-js" lang="js">JavaScript</live-example>代码**

a(id="modularity")
.l-main-section
:marked
  ## Importing and Exporting

  ## 导入与导出

- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
  col(width="50%")
  tr
    th TypeScript
    th ES5 JavaScript
  tr(style=top)
    td
      :marked
        ### Importing Angular 2 Code

        ### 导入Angular 2代码

        In TypeScript code, Angular 2 classes, functions, and other members
        are imported with TypeScript `import` statements:
        
        在TypeScript代码中，Angular 2是利用TypeScript的`import`语句来导入类、函数和其他成员的。

      +makeExample('cb-ts-to-js/ts/app/main.ts', 'ng2import')(format="." )

    td
      :marked
        ### Accessing Angular 2 Code through the ng global
        
        ### 通过全局变量`ng`来访问Angular 2代码

        In JavaScript code, when using
        [the Angular 2 packages](../glossary.html#!#scoped-package),
        we can access Angular code through the global `ng` object. In the
        nested members of this object we'll find everything we would import
        from `angular2` in TypeScript:
        
        在JavaScript中，当使用[Angular 2库](../glossary.html#!#scoped-package)时，
        我们可以通过全局的`ng`对象来访问Angular代码。在本对象内嵌的很多成员中，我们会发现TypeScript能从`@angular`库导入的所有对应物。

      +makeExample('cb-ts-to-js/js/app/main.js', 'ng2import')(format="." )

  tr(style=top)
    td
      :marked
        ### Importing and Exporting Application Code

        ### 导入与导出应用程序代码

        Each file in an Angular 2 TypeScript application constitutes a
        TypeScript module. When we want to make something from a module available
        to other modules, we `export` it.
        
        在TypeScript版的Angular 2程序里，每个文件都是一个TypeScript模块。当需要让一个模块在其它模块中可见时，我们要`export`它。

      +makeExample('cb-ts-to-js/ts/app/hero.component.ts', 'appexport')(format="." )

      :marked
        In other modules we can then `import` things that have been exported
        elsewhere.
        
        然后，我们就可以在其它模块中`import`这些在别处导出的东西。

      +makeExample('cb-ts-to-js/ts/app/main.ts', 'appimport')(format="." )

    td
      :marked
        ### Sharing Application Code

        ### 共享应用程序代码

        In an Angular 2 JavaScript application, we load each file to the page
        using a `<script>` tag. Each file can make things available to other
        files via the shared global `window` scope.
        
        在JavaScript版的Angular 2程序里，我们在页面中通过`<script>`标签来加载每个文件。
        每个文件都要通过全局作用域`window`来互相共享自己的那些东西。

        We often introduce an application namespace
        object (such as `"app"`) onto `window` and attach everything we need
        to share to that namespace object. 
        We also wrap our code in an 
        [Immediately Invoked Function Expression (IIFE)](https://en.wikipedia.org/wiki/Immediately-invoked_function_expression).
        These practices together prevent our code from
        polluting the global scope.
        
        我们经常在`window`对象上附加一个应用程序命名空间对象(比如`"app"`)，然后把所要共享一切都附加到这个对象上。
        也可以把我们的代码包装进一个[立即调用函数表达式IIFE](https://en.wikipedia.org/wiki/Immediately-invoked_function_expression)。
        这些实践可以防止我们的代码污染全局作用域。

      +makeExample('cb-ts-to-js/js/app/hero.component.js', 'appexport')(format="." )

      :marked
        We can then access anything from this shared namespace in
        other files.
        
        然后我们就可以用这个共享的命名空间来访问来自其它文件中的东西了。

      +makeExample('cb-ts-to-js/js/app/main.js', 'appimport')(format="." )

      :marked
        Note that the order of `<script>` tags on the page is significant. 
        We must load a file that defines a shared member before
        a file that uses that member.
        
        注意，页面中`<script>`标签的排列顺序非常重要。我们必须要先加载“定义”共享成员的文件，
        然后再加载“使用”该共享成员的文件。

.alert.is-helpful
  :marked
    Alternatively, we can use a module loader such as Webpack or
    Browserify in an Angular 2 JavaScript project. In such a project, we would
    use CommonJS modules and the `require` function to load Angular 2 framework code.
    We would then use `module.exports` and `require` to export and import application
    code.
    
    另外，我们可以在JavaScript版的Angular 2项目中，使用模块加载器(比如Webpack或者Browserify)。
    在这样的项目中，我们使用CommonJS模块和`require`函数来加载Angular 2框架代码。
    然后用`module.exports`和`require`来导出和导入应用程序代码。


a(id="class-metadata")
.l-main-section
:marked
  ## Classes and Class Metadata

  ## 类和“类的元数据”

- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
  col(width="50%") 
  tr
    th TypeScript
    th ES5 JavaScript
  tr(style=top)
    td
      :marked
        ### Classes
        
        ### 类

        We put most of our Angular 2 TypeScript code into TypeScript classes.
        
        在Angular 2中，我们把绝大多数TypeScript代码都放到TypeScript类中。

      +makeExample('cb-ts-to-js/ts/app/hero.component.ts', 'class')(format="." )

    td
      :marked
        ### Constructors and Prototypes

        ### 构造函数和原型

        ES5 JavaScript has no classes. We use the constructor
        pattern instead which works with Angular 2 as well as classes do.
        
        ES5 JavaScript不支持类，我们使用构造器模式(constructor pattern)来代替它，它可以和类一样与Angular 2协同工作。

      +makeExample('cb-ts-to-js/js/app/hero.component.js', 'constructorproto')(format="." )

  tr(style=top)
    td
      :marked
        ### Metadata with Decorators
        ### 使用装饰器提供元数据

        Most Angular 2 classes have one or more TypeScript *decorators*
        attached to provide configuration and metadata. For example,
        a component must have a [`@Component`](../api/core/index/Component-decorator.html) decorator.
        
        大部分Angular 2中的类都会附加一个或多个TypeScript*装饰器*，用来提供配置和元数据。比如组件必须要有一个[`@Component`](../api/core/index/Component-decorator.html)装饰器。
        

      +makeExample('cb-ts-to-js/ts/app/hero.component.ts', 'metadata')(format="." )

    td
      :marked
        ### Metadata with the Annotations Array        
        
        ### 通过注解数组来提供元数据        

        In JavaScript, we can attach an `annotations` array to a constructor
        to provide metadata. 
        Each item in the array corresponds to a TypeScript decorator.
        
        在JavaScript中，我们可以为构造函数附加一个`注解`数组来提供元数据。
        数组里的每一个条目都对应一个TypeScript装饰器。

        In the following example, we create a new instance of `Component` that corresponds
        to the [`@Component`](../api/core/index/Component-decorator.html) TypeScript decorator.
        
        在下面的例子中，我们新建了一个`Component`的新实例，与[`@Component`](../api/core/index/Component-decorator.html)TypeScript装饰器相对应。

      +makeExample('cb-ts-to-js/js/app/hero.component.js', 'metadata')(format="." )

      :marked
        ### Metadata with The Class Convenience API
        
        ### 利用便捷API `Class`提供元数据

        The pattern of creating a constructor and decorating it with metadata
        is so common that Angular provides an alternative convenience API for it.
        This API lets us define everything in a single expression.
        
        创建一个构造函数并用元数据来装饰它，这种模式非常常见，以至于Angular为它提供了一个可选的便捷API。
        该API让我们能在单一表达式中定义任何东西。

        With this API we first call the `ng.core.Component` function,
        followed by a chained `Class` method call. The argument to `Class`
        is an object that defines the constructor and the instance methods
        of the component:
        
        利用该API，我们先调用`ng.core.Component`函数，再链式调用一个`Class`方法。该`Class`方法的参数是一个对象，
        用来定义组件的构造函数和实例方法。

      +makeExample('cb-ts-to-js/js/app/hero-dsl.component.js', 'component')(format="." )

      :marked
        Similar APIs are also available for other decorators. You can define a
        directive:
        
        其它装饰器也都有类似的API。比如你可以像这样定义指令：
        
      code-example.
        var MyDirective = ng.core.Directive({
          ...
        }).Class({
          ...
        });
      
      :marked
        Or a pipe:
        
        或者一个管道：
        
      code-example.
        var MyPipe = ng.core.Pipe({
          name: 'myPipe'
        }).Class({
          ...
        });

  tr(style=top)
    td
      :marked
        ### Interfaces
        
        ### 接口

        When defining classes that need to implement a certain method, it
        is common to use TypeScript interfaces that enforce that the 
        method signature is correct. Component lifecycle methods like `ngOnInit`
        are one example of this pattern. `ngOnInit` is defined in the `OnInit`
        interface.
        
        当定义一个想实现某个方法的类时，常用TypeScript接口来确保方法的签名正确。组件生命周期方法，比如`ngOnInit`就是一个例子。
        `ngOnInit`是在`OnInit`接口里面定义的。

      +makeExample('cb-ts-to-js/ts/app/hero-lifecycle.component.ts')(format="." )

    td
      :marked
        ### Implementing Methods without Interfaces
        
        ### 实现方法，但不用管接口

        TypeScript interfaces are purely for developer convenience
        and are not used by Angular 2 at runtime. This means that in JavaScript
        code we don't need to substitute anything for interfaces. We can just
        implement the methods.
        
        TypeScript的接口纯粹是为了方便开发者而设计的，它不能被Angular 2在运行时使用。这就意味着在JavaScript代码里，
        我们不需要使用任何东西来代替接口。我们只要直接实现它的方法就行了。

      +makeExample('cb-ts-to-js/js/app/hero-lifecycle.component.js')(format="." )

a(id="property-metadata")
.l-main-section
:marked
  ## Input and Output Metadata
  
  ## `Input`(输入)和`Output`(输出)元数据

- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
  col(width="50%") 
  tr
    th TypeScript
    th ES5 JavaScript
  tr(style=top)
    td
      :marked
        ### Input and Output Decorators
        
        ### `Input`(输入)和`Output`(输出)装饰器

        In TypeScript, property decorators are often used to provide additional metadata
        for components and directives.
        
        在TypeScript里，属性装饰器经常被用来为组件和指令提供额外的元数据。

        For [inputs and outputs](../guide/template-syntax.html#inputs-outputs), 
        we use [`@Input`](../api/core/index/Input-var.html)
        and [`@Output`](../api/core/index/Output-var.html) property decorators.
        They may optionally specify input and output binding names if we want them to be
        different from the class property names.
        
        我们使用[`@Input`](../api/core/index/Input-var.html) 和 [`@Output`](../api/core/index/Output-var.html)装饰器
        来装饰[输入属性与输出属性](../guide/template-syntax.html#inputs-outputs)。
        如果想让它们的名字与类属性名不同，我们可以(可选的)指定输入和输出的绑定名。

      +makeExample('cb-ts-to-js/ts/app/hero-io.component.ts')(format="." )

      .alert.is-helpful
        :marked
          In TypeScript we can also use the `inputs` and `outputs` array metadata 
          instead of the `@Input` and `@Output` property decorators.
          
          在TypeScript里，我们同样可以使用`inputs`和`outputs`元数据数组，来代替`@Input`和`@Output`属性装饰器。
    td
      :marked
        ### Inputs and Outputs in Component Metadata
        
        ### 组件元数据里的输入属性和输出属性

        There is no equivalent of a property decorator in ES5 JavaScript. Instead, 
        we add comparable information to the `Component` (or `Directive`) metadata.
        
        在ES5 JavaScript里并没有属性装饰器的等价物，但我们可以往`Component`(或者`Directive`)的元数据中添加对应的信息。
        
        In this example, we add `inputs` and `outputs` array attributes
        containing the input and output property names. 
        If we need a binding name that is different from the
        property itself, we use the `propertyName: bindingName` syntax.
        
        在这个例子中，我们添加了`inputs`和`outputs`数组属性，它们包含了输入属性名和输出属性名。
        如果我们需要一个不同于属性名的绑定名，可以使用`propertyName: bindingName`的语法。

      +makeExample('cb-ts-to-js/js/app/hero-io.component.js')(format="." )


.l-main-section
:marked
  ## Dependency Injection
  
  ## 依赖注入

- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
  col(width="50%") 
  tr
    th TypeScript
    th ES5 JavaScript
  tr(style=top)
    td
      :marked
        ### Injection by Type
        
        ### 按类型注入 

        Angular 2 can often use TypeScript type information to
        determine what needs to be injected.
        
        Angular 2通常使用TypeScript的类型信息来确定需要注入什么。

      +makeExample('cb-ts-to-js/ts/app/hero-di.component.ts')(format="." )

    td
      :marked
        ### Injection with Parameter Tokens
        
        ### 使用参数指令来注入

        Since no type information is available in ES5 JavaScript,
        we must identify "injectables" in some other way.
        
        由于在ES5 JavaScript里没有类型信息，所以我们必须使用其它方法来标记出“可供注入”的东西。

        We attach a `parameters` array to the constructor function. 
        Each array item is the dependency injection token that identifies the thing to be injected. 
        Often the token is the constructor function for the class-like dependency.
        
        我们可以为构造函数附加一个`parameters`数组。数组中的每个条目都是一个“依赖注入令牌”，用来标识出希望被注入进来的东西。
        通常，对于“类”依赖，这个令牌就是它的构造函数。

      +makeExample('cb-ts-to-js/js/app/hero-di.component.js')(format="." )

      :marked
        When using the class convenience API, we can also supply the parameter
        tokens by wrapping the constructor in an array.
        
        当我们使用便捷API `Class`时，也可以把构造器包装到一个数组里面来提供参数令牌。

      +makeExample('cb-ts-to-js/js/app/hero-di-inline.component.js')(format="." )

  tr(style=top)
    td
      :marked
        ### Injection with the @Inject decorator
        
        ### 使用`@Inject`装饰器来注入

        When the thing being injected doesn't correspond directly to a type,
        we use the `@Inject()` decorator to supply the injection token.
        
        当被注入的东西不是一个类型时，要使用`@Inject()`装饰器来提供注入令牌。
        
        In this example, we're injecting a string identified by the "heroName" token.
        
        在下面这个例子中，我们用令牌"heroName"注入了一个字符串。

      +makeExample('cb-ts-to-js/ts/app/hero-di-inject.component.ts')(format="." )

    td
      :marked
        ### Injection with plain string tokens
        
        ### 利用普通字符串令牌来注入

        In JavaScript we add the token string to the injection parameters array.
        
        在JavaScript中，我们要把令牌字符串添加到注入参数的数组中。

      +makeExample('cb-ts-to-js/js/app/hero-di-inject.component.js','parameters')(format="." )
      
      :marked
        Alternatively, we can create a token with the `Inject` method and
        add that to the constructor array in the annotations like this:
        
        另外，我们可以使用`Inject`方法新建一个令牌，然后把它加到注解里的constructor数组中，就像这样：
        
      +makeExample('cb-ts-to-js/js/app/hero-di-inject.component.js','ctor')(format="." )        

  tr(style=top)
    td
      :marked
        ### Additional Injection Decorators
        
        ### 额外的注入装饰器

        We can attach additional decorators to constructor parameters
        to qualify the injection behavior. We can mark
        optional dependencies with the [`@Optional`](../api/core/index/Optional-var.html),
        inject host element attributes with [`@Attribute`](../api/core/index/Attribute-var.html),
        inject content child queries with [`@Query`](../api/core/index/Query-var.html)
        and inject view child queries with [`@ViewQuery`](../api/core/index/ViewQuery-var.html).
        
        我们可以往构造函数中附加额外的装饰器来调整注入行为。比如使用[`@Optional`](../api/core/index/Optional-var.html)来标记依赖是可选的，
        用[`@Attribute`](../api/core/index/Attribute-var.html)来注入宿主元素的属性(Attribute)，
        用[`@Query`](../api/core/index/Query-var.html)来注入投影内容的子查询，用[`@ViewQuery`](../api/core/index/ViewQuery-var.html)来注入视图的子查询。

      +makeExample('cb-ts-to-js/ts/app/hero-di-inject-additional.component.ts')(format="." )

    td
      :marked
        ### Additional Injection Metadata with Nested Arrays 
        
        ### 利用嵌套数组来添加额外的注入元数据

        To achieve the same effect in JavaScript, use the constructor array notation
        in which the injection information precedes the constructor function itself.
        
        在JavaScript中，为了达到同样的效果，要使用构造器数组表示法，其中的注入信息优先于构造函数自身的。
        
        Use the injection support functions `Attribute`, `Host`, `Optional`, `Self`, `SkipSelf` to qualify dependency injection behavior.

        使用“注入支持函数”，比如`Attribute`、 `Host`、 `Optional`、 `Self`、 `SkipSelf`、`Query` 和 `ViewQuery`等来调整依赖注入的行为。
        
        Use a nested array to combine injection functions.
        
        使用嵌套数组来合并注入函数。

      +makeExample('cb-ts-to-js/js/app/hero-di-inject-additional.component.js')(format="." )

      :marked
        We can apply other additional parameter decorators such as
        [`@Host`](../api/core/index/Host-var.html) and
        [`@SkipSelf`](../api/core/index/SkipSelf-var.html) in the same way -
        by adding `new ng.core.Host()` or `ng.core.SkipSelf()` in the
        parameters array.
        
        我们可以用同样的方法来使用其它的额外参数装饰器，比如[`@Host`](../api/core/index/Host-var.html) 和
        [`@SkipSelf`](../api/core/index/SkipSelf-var.html)：往参数数组中添加`new ng.core.Host()` 或 `ng.core.SkipSelf()`。


a(id="other-property-metadata")
.l-main-section
:marked
  ## Host and Query Metadata
  
  ## `Host`(宿主)与`Query`(查询)元数据

- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
  col(width="50%") 
  tr
    th TypeScript
    th ES5 JavaScript  
  tr(style=top)
  
    td
      :marked
        ### Host Decorators
        
        ### `Host`(宿主)装饰器

        We can use host property decorators to bind a host element to a component or directive.
        The [`@HostBinding`](../api/core/index/HostBinding-var.html) decorator
        binds host element properties to component data properties. 
        The [`@HostListener`](../api/core/index/HostListener-var.html) decorator bimds
        host element events to component event handlers.
        
        我们可以使用宿主属性装饰器来把宿主元素绑定到组件或指令。
        [`@HostBinding`](../api/core/index/HostBinding-var.html)装饰器把宿主元素的属性绑定到组件的数据属性。
         [`@HostListener`](../api/core/index/HostListener-var.html)装饰器把宿主元素的事件绑定到组件的事件处理器。
        
      +makeExample('cb-ts-to-js/ts/app/heroes-bindings.component.ts')(format="." )
      
      .alert.is-helpful
        :marked
          In TypeScript we can also use `host` metadata 
          instead of the `@HostBinding` and `@HostListener` property decorators.
          
          在TypeScript中，我们也可以用`host`元数据来代替`@HostBinding`和`@HostListener`属性装饰器。
    td
      :marked
        ### Host Metadata
        
        ### Host元数据
        
        We add a `host` attribute to the component metadata to achieve the
        same effect as `@HostBinding` and `@HostListener`.
        
        我们添加一个`host`属性到组件的元数据，以达到和`@HostBinding`、`@HostListener`一样的效果。 
        
        The  `host` value is an object whose properties are host property and listener bindings:
        
        `host`的值是一个对象，它的属性中包含了宿主属性和事件监听器的绑定。
        
        * Each key follows regular Angular 2 binding syntax: `[property]` for host bindings
          or `(event)` for host listeners.
          
        * 每个键值(key)都遵循常规的Angular 2绑定语法：用`[property]`代表宿主属性绑定，用`(event)`代表数组事件绑定。
        
        * Each value identifies the corresponding component property or method.
        
        * 每个值(value)代表了对应的组件属性或方法。
        
      +makeExample('cb-ts-to-js/js/app/heroes-bindings.component.js')(format="." )

  tr(style=top)
    td
      :marked
        ### Query Decorators
        
        ### `Query`(查询)装饰器
        
        There are several property decorators for querying the descendants of
        a component or directive.
        
        有好几个属性装饰器可以用来查询组件或指令的各级子节点。
        
        The [`@ViewChild`](../api/core/index/ViewChild-var.html) and
        [`@ViewChildren`](../api/core/index/ViewChildren-var.html) property decorators
        allow a component to query instances of other components that are used in
        its view.
        
        [`@ViewChild`](../api/core/index/ViewChild-var.html)和
        [`@ViewChildren`](../api/core/index/ViewChildren-var.html)属性装饰器允许组件查询
        在自己模板里用到的其它组件实例。
        
        
      +makeExample('cb-ts-to-js/ts/app/heroes-queries.component.ts', 'view')(format="." )

      :marked
        The [`@ContentChild`](../api/core/index/ContentChild-var.html) and
        [`@ContentChildren`](../api/core/index/ContentChildren-var.html) property decorators
        allow a component to query instances of other components that have been projected
        into its view from elsewhere.
        
        [`@ContentChild`](../api/core/index/ContentChild-var.html) 和
        [`@ContentChildren`](../api/core/index/ContentChildren-var.html)属性装饰器允许组件查询那些从其它地方投影到自己视图里的其它组件实例。
        
      +makeExample('cb-ts-to-js/ts/app/heroes-queries.component.ts', 'content')(format="." )
      
      .alert.is-helpful
        :marked
          In TypeScript we can also use the `queries` metadata 
          instead of the `@ViewChild` and `@ContentChild` property decorators.
          
          在TypeScript中，我们也可以使用`queries`元数据来代替`@ViewChild`和`@ContentChild`属性装饰器。      
    td
      :marked
        ### Query Metadata
        
        ### `Query`(查询)元数据
        
        We access a component's view children by adding a `queries` attribute to
        the component metadata. It should be an object where:
        
        我们通过往组件元数据中添加`queries`属性来访问一个组件的各级子节点。它应该是一个对象，其中：
        
        * Each key is the name of a component property that will hold the view children
        
        * 每个键值(key)都是组件中的一个属性名，该属性用来保存当前视图的子节点。
        
        * Each value is an instance of either `ViewChild` or `ViewChildren`.
        
        * 每个值都是一个`ViewChild`或者`ViewChildren`的实例。
        
      +makeExample('cb-ts-to-js/js/app/heroes-queries.component.js', 'view')(format="." )

      :marked
        We add *content* child queries to the same `queries` attribute
        in the same manner, using instances of `ContentChild` or `ContentChildren`:
        
        同样的，我们利用`ContentChild`和`ContentChildren`往`queries`属性中添加*投影内容*的子查询：
        
      +makeExample('cb-ts-to-js/js/app/heroes-queries.component.js', 'content')(format="." )
